The present invention relates to an apparatus and method for stretching a film simultaneously in two (biaxial) directions (e.g., both the film travel direction and the film width direction).
In Japanese Laid-open patent No. 4 - 12957, one guiding mechanism for a simultaneous biaxial stretching machine for a film is disclosed. The guiding mechanism is composed of a roll bearing that rolls between vertical side walls of a guidance groove and a thrust bearing which receives a link weight for sliding on a bottom surface in the guidance groove.
Another example of a guiding mechanism for a width stretching machine is disclosed in the Japanese Laid-Open Utility Model No. 1987 - 147520. The disclosed structure has a roll bearing that travels along a guidance rail while receiving its own weight and a roll bearing that guides along the guidance rail.
In the above disclosure, because the weight of a whole link is large, running friction or sliding friction caused by supporting the weight of the link in the operation mode is also large. It is difficult to drive the link at high speed travel. In addition, there is a problem of scattering lubricant to the film, which is a cause of dirt, because of the necessity of applying a lubricant to the slide part.
A complex structure is required in order to combine the roll bearing used in the width stretching machine into the simultaneous biaxial stretching machine. However, it is actually difficult to adopt it, since a thrust load which acts on the roll bearing shortens the life of the roll bearing and a rail.